The present invention relates to a time lock. More particularly this invention concerns a time lock used in conjunction with the lock mechanism of a vault door.
A strong room or vault is provided with a door having an extensive and heavy-duty lock mechanism. A plurality of bolts can be extended outwardly into the jamb receiving the edge of the door, controlled by an actuating mechanism in turn operated by means of a key- or combination-controlled lock. The time lock itself is connected to the actuating mechanism and is provided normally inside the vault, safe or strong box. Before the door is closed the timer of such a time lock is set so that even if the proper combination or key is employed, it is impossible to open the safe or strong room door before the set interval has elapsed.
Normally such a time lock is provided in the path of a bolt or other part of the lock mechanism for the safe. Before elapsing of the set time a keeper or bolt of the time lock is positioned in the path of the lock part so that it cannot be moved in the manner necessary to open the door that is locked. Only when the set time has elapsed does this keeper withdraw and unblock the lock part so that the lock mechanism can be operated to open the door.
Normally such a device has a pair of lock members, one of which is formed with a recess and the other of which is formed as a pawl engageable in this recess and connected to the keeper that can block the path of the bolt of the lock mechanism. When the set time has elapsed the recess is aligned by a clockwork of the time lock with the pawl so that this pawl can drop into the recess and allow the keeper to move out of the way of the bolt of the lock mechanism. The lock member with the pawl is normally slidable by the clockwork into a position with its recess aligned with the above-mentioned pawl.
It is normally essential to minimize the resistance that the lock member offers to the clockwork, so that the clockwork can be made as sensitive as possible and it therefore need not push against a relatively heavy mass. When, however, the lock member is made too light, it is possible for a skilled safe cracker to actuate the mechanism by jarring the time lock from the side so as to slide this lock member in the necessary direction to align its recess with the pawl. Thus it is necessary to provide a relatively heavy biasing spring preventing such unauthorized use, so that the clockwork or clockworks must operate against a relatively heavy force.
Another disadvantage of the known systems is that it is necessary not only to wind up the clockworks of the time lock before closing the safe or strong room, but it is also necessary to set the time lock. Such setting normally consists in displacing by means of a lever or knob the lock member having the recess into a position with its recess out of line with the pawl, simultaneously pulling the pawl out of this recess. Thus a frequent occurrence is that the time lock is not properly set, a condition which cannot be detected once the safe is closed, thereby almost completely eliminating the effectiveness of this type of arrangement.